ON THE CONSERVATION OF FORCE. 307 



quantity of heat is nothing more than the whole motive power 

 of the motion of heat, which remains constant so long as it is not 

 transformed into other forms of work, or results afresh from them. 



We turn now to another kind of natural forces which can 

 produce work I mean the chemical. We have to-day already 

 come across them. They are the ultimate cause of the work 

 which gunpowder and the steam-engine produce; for the heat 

 which is consumed in the latter, for example, originates in the 

 combustion of carbon that is to say, in a chemical process. The 

 burning of coal is the chemical union of carbon with the oxygen 

 of the air, taking place under the influence of the chemical 

 affinity of the two substances. 



We may regard this force as an attractive force between the 

 two, which, however, only acts through them with extraordinary 

 power, if the smallest particles of the two substances are in 

 closest proximity to each other. In combustion this force acts ; 

 the carbon and oxygen atoms strike against each other and 

 adhere firmly, inasmuch as they form a new compound carbonic 

 acid a gas known to all of you as that which ascends from all 

 fermenting and fermented liquids from beer and champagne. 

 Now this attraction between the atoms of carbon and of oxygen 

 performs work just as much as that which the earth in the 

 form of gravity exerts upon a raised weight. When the weight 

 falls to the ground, it produces an agitation, which is partly 

 transmitted to the vicinity as sound waves, and partly remains 

 as the motion of heat. The same result we must expect 

 from chemical action. When carbon and oxygen atoms have 

 rushed against each other, the newly-formed particles of carbonic 

 acid must be in the most violent molecular motion that is, in 

 the motion of heat. And this is so. A pound of carbon burned 

 with oxygen to form carbonic acid, gives as much heat as is 

 necessary to raise 80 -9 pounds of water from the freezing to 

 the boiling point ; and just as the same amount of work is pro- 

 duced when a weight falls, whether it falls slowly or fast, so also 

 the same quantity of heat is produced by the combustion of 

 carbon, whether this is slow or rapid, whether it takes place all 

 at once, or by successive stages. 



